Rotary piston blower with mechanical and pneumatic compression



c. HUBRICH Aug. 2, 1966 ROTARY PISTON BLOWER WITH MECHANICAL ANDPNEUMATIC COMPRESSION Filed Nov. 1, 1965 5 Sheets-Sheet 1 INVENTOR.Christoph Hubrich C. HUBRICH Aug. 2, 1966 ROTARY PISTON BLOWER WITHMECHANICAL AND PNEUMATIC COMPRESSION Filed Nov. 1, 1963 3 Sheets-Sheet 2Fig. 2

INVENTOR. Christoph Hub/id;

C. HUBRICH Aug. 2, 1966 ROTARY PISTON BLOWER WITH MECHANICAL ANDPNEUMATIC COMPRESSION Filed NOV.

5 Sheets-Sheet 5 INVENTOR. Chrisfaph l-lu brl'ch United States Patent"ice 3,263,911 ROTARY PISTON BLOWER WITH MECHANICAL AND PNEUMATICCOMPRESSION Christoph Hubrich, Offenbach (Main)-Bieber, Germany,assignor to Polysius G.m.b.H., Neubeckum, Germany Filed Nov. 1, 1963,Ser. No. 320,895 3 Claims. (Cl. 230-138) The present invention relatesto a rotary piston blower with interengaging rotary pistons. Blowers ofthis type have in addition to various advantages one foremostdisadvantage, as will presently appear. When the rotary piston duringits rotation passes beyond the edge of the outlet so that the conveyingchamber containing air at the initial pressure communicates with thepressure chamber, compressed air rushes from the outlet into theconveying chamber and while losing a part of its pressure increases thepressure of the air in said chamber. As a result thereof the degree ofefliciency considerably decreases relative to the ideal adiabatic strokepiston degree of efficiency. This drop in efficiency increases withincreasing pressure ratio between the air pressure at said outlet andthe air pressure in said chamber so that at a certain pressure ratio (inpractice about 1.8) the upper limit of economy has been reached. In thepast, attempts have been made by various designs, such as the Ljungstromor Zoller-Wittich blowers, or by the selection of non-symmetric oruneven rotary piston shapes to overcome the above-mentioned drawback ofrotary piston blowers. These endeavors have led more and more away fromthe simple lemniscate shape of the original Roots rotary piston. Thethus created rotary piston designs are considerably more diflicult tomachine and greatly complicate the heretofore simple structure.

It is, therefore, an object of the present invention to provide a methodof improving the efficiency of rotary piston blowers.

It is also an object of this invention to provide a rotary piston blowerwith inner compression in the fluid conveying chamber while retainingthe original lemniscate shape of the original Roots rotary piston.

These and other objects and advantages of the invention will appear moreclearly from the following specification in connection with theaccompanying drawings, in which FIGS. l to 3 diagrammatically show arotary piston blower according to the present invention in threeconsecutive stages of operation.

The method according to the present invention is characterized primarilyin that the fluid which with each cycle of the blower is conveyed froman inlet to an outlet has its pressure increased prior to the said fluidreaching said outlet. This method may be carried out by a rotary pistonblower in which a plurality of rotatable main pistons cooperate with thehousing means of the blower so as to confine delivery chamber means andto convey therein fluid from the inlet to the outlet of the housing,while rotatable auxiliary piston means are provided which are adapted incooperation with the main pistons to compress fluid in said deliverychamber means prior to said main pistons releasing fluid from thedelivery chamber means to said outlet. The said main pistons may haveany lemniscate profile while the auxiliary piston means may have thesame profile as the main pistons up to their outer radius where theircontour rnenges into a circular contour. However, two diagrammaticallyoppositely located edges of said auxiliary piston means have beenrounded off.

Referring now to the drawing in detail and FIG. 1 thereof in particular,the arrangement shown therein comprises a housing 1 having rotatablymounted therein a rotary piston 2 and a rotary piston 3. Pistons 2 and 3may henceforth be called main rotary pistons. These two main rotarypistons 2 and 3 are so contoured that'at all 3 ,Z63,9l l Patented August2, 1966 times they sealingly engage each other so as to prevent, incooperation with other sealing elements to be described further below,the direct flow of fluid within the housing from an inlet 6 to an outlet7. Each of the pistons 2 and 3 is, furthermore, so contoured as toengage the surface In and 1b respectively of the housing 1 in such a waythat at all times one surface portion of the main pistons 2 and 3sealingly engages the respective housing surfaces 1a, 1b.

The main rotary pistons 2 and 3 are drivin-gly interconnected in anyconvenient manner, for instance by gears 2a, 2b (indicated by dot-dashlines only).

Cooperating with the main pistons 2 and 3 are two rotatable auxiliarypistons 4 and 5 respectively, which are drivingly connected, forinstance by gears, to the main pistons 2 and 3, respectively. Thedriving connection may be such that the auxiliary pistons 4 and 5 rotateat the same speed as the main pistons 2 and 3.

As to the contour of the auxiliary pistons 4 and 5, it will be seen fromthe drawing that each tooth 4a, 4b; 5a, 5b has a sharp-edged portion 10,11; 12, 13 and a rounded portion 10a, 11a; 12a, 13a. The sharp-edgedportions 10, 11; 12, 13 serve so-to-speak as scoops, for a purpose whichwill appear more clearly as the description proceeds. Moreover, thecountour sections 22, 21 between portions 10, 10a and 11, 11a ofauxiliary piston 4 and, similarly, the contour sections between theportions 12 and 12a, 16 and 13a of auxiliary piston 5 are such that atleast a portion thereof will, during each rotation of the respectiveauxiliary pistons, sealingly engage the respective adjacent housingsurfaces lc, 1d. The contour sections 19 between the portions 10a and 11and also the contour sections 20 between 10 and 10a are such as, duringeach rotation of auxiliary piston 4, to temporarily sealingly engage themain piston 2 (see, for instance FIGS. 1 and 2). The correspondingportions of auxiliary piston 5 are, of course, similarly designed fortemporary sealing engagement with the main piston 3. Sections 19 and 20of piston 4 which engage piston 2 have a contour shaped in conformitywith corresponding sections 18, 1811 on piston 2, the respective lengthof these sections being indicated by dash lines.

As will be evident from the above, the various pistons form with thehousing a plurality of chambers 8, 9, 14, 15 and 1 6 which, during theoperation of the blower, vary in shape and location. In additionthereto, the various pistons confine with each other and housingportions a chamber 17 which always communicates with the outlet 7 butwhich also varies in shape during the operation of the blower. Pistons 2and 3 rotate about axes 27 and 28 respectively, while pistons 4 and 5rotate about axes 25 and 26 respectively, the spacing between axes 25,27; 27, 28; and 28, 26 being the same.

Operation Referring first to the state of operation of the blower asillustrated in FIG. 1, the chamber 8 has just been completely closed offfrom inlet 6. At this stage, chamber 8 containing air of the samepressure condition as it prevails at the inlet 6, becomes a delivery orconveying chamber since, as will be seen from FIG. 3, it will eventuallydeliver the air enclosed in chamber 8 into the pressure chamber 17 andto the outlet 7.

In FIG. 1 position, piston 4 has completely closed chamber 16 withregard to chamber 17. No work will be performed for the transport of theair in chamber 16 from FIG. 1 position to FIG. 3 position inasmuch as nocompression of the air in chamber 16 takes place.

The air in chamber 14 was previously compressed in a manner which is notillustrated in FIGS. 1 to 3 for pistons 2 and 4 but is shown therein forpistons 3 and 5. Since the operation of pistons 2 and 4 is identical tothat of pistons 3 and with the exception that pistons 3 and 5 reach thepositions of pistons 2 and 4 at a different time, the compression inchamber 14 may be explained in connection with the operation of pistons3 and 5 in FIGS. 1 to 3. When piston 4 moves in the direction of thearrow indicated thereon, chamber 16 will communicate with the pressurechamber 17 in a manner similar to that in which chamber 15 in FIGS. 1and 2 communicates with chamber 17 through chamber 9. Thereupon, chamber14 will be closed off from pressure chamber 17 in a manner analogous tochamber 15 being closed ofi from chamber 17 in FIG. 3, and the airtherein is compressed to a pressure higher than that prevailing inchamber 17.

When the pistons 2 and 4 move into their FIG. 1 positions, the mainpiston 2 opens up a communication between the chambers 8 and 14. As aresult thereof, the air in chamber 14 of higher pressure than in chamber17 brings about a pneumatic compression of the air in the deliverychamber 8. Since auxiliary piston 4 continues its rotative movementindicated by the arrow thereon, it so-to-speak moves into chamber 8, andsince piston 4 still sealingly engages piston 2 and a section of thehousing surface 10, piston 2 mechanically compresses the air in chamber8. The air in chamber 8 is compressed to a pressure which preferablyequals or exceeds the pressure in pressure chamber 17.

When pistons 2 and 4 have reached their FIG. 3 position, they haveopened a passage therebetween through which the chamber 8 communicateswith the pressure chamber 17. In the course of the further rotarymovement of piston 2, as indicated by the arrow thereon, and the rotarymovement of piston 4 in the direction of the arrow on the latter,communication is established between the chambers 8 and 16, and bothpistons now displace air from chambers 8 and 1 6 into pressure chamber17.

In the course of a rotation of 360 of each piston, the phase ofoperation of FIGS. 1 to 3 will be repeated four times, in the samesequence.

It will be appreciated that the scoop shape of the sharp-edged portionsof piston 4 aids in displacing and entrapping of air from and in thechambers partially formed by piston 4.

While the above description referred only to pistons 2 and 4 of theblower according to the invention, it will be appreciated that theoperation of the pistons 3 and 5 is precisely the same as that ofpistons 2 and 4.

As will be evident from the above description, by increasing anddecreasing the size of the auxiliary pistons 4 and 5 as well as by asuper-compression in the chamber 1 4, as described above in connectionwith FIG. 4, i.e. by an earlier sealing engagement between the pistons 2and 4, any desired end compression will be obtainable in the deliverychamber 8. Whereas with heretofore known blowers, the isochoric degreeof efliciency of the blower will, in comparison to the ideal adiabaticdegree of efliciency, drop already at a pressure ratio of 1.7 by 20% andat a pressure ratio of 2.5 by 30%, the present invention obviates thisloss to at least a great extent.

While in the preceding description, reference is made to a sealingengagement between the pistons, it is to be understood that, as is wellknown in connection with rotary piston blowers, an actual contactbetween the rotors must not take place. Instead, at each socalledposition of'sealing engagement, the pistons are spaced from each otherby a fraction of a millimeter. This spacing, however, which may betermed play, has been disregarded in the preceding description of theoperation.

It is, of course, to be understood that the present invention, is by nomeans limited to the particular design as described above, but alsocomprises any modifications within the scope of the appended claims.

What I claim is:

1. In a rotary blower: housing means having fluid inlet means and fluidoutlet means, two main piston means rotatable within said housing means,and two auxiliary piston means rotatable withinsaid housing means inaxially spaced relationship to said main piston means and at the samespeed as the latter for respective cooperation with said main pistonmeans, said main piston means being rotatable in opposite direction withregard to each other, and each auxiliary piston means being rotatable ina direction opposite to the direction of rotation of the respective mainpiston means cooperating therewith, each of said rotatable main pistonmeans being adapted with a respective first section of said housingmeans to form main chamber means adapted to receive and entrap fluidfrom said inlet means, each of said auxiliary piston means beingoperable in response to a first position thereof relative to therespective main piston means cooperating therewith to form with saidmain piston means and with a respective adjacent second sectionof saidhousing means first auxiliary chamber means adapted to receive fluidfrom said outlet means, each of said auxiliary piston means also beingoperable with a respective adjacent third section of said housing meansto form second auxiliary chamber means adapted to receive and entrapfluid from said out-' let means, each of said auxiliary piston meansbeing operable in response to a second relative position thereof withregard to the respective main piston means cooperating therewith torelease fluid from the respective first auxiliary chamber means to therespective main chamber means pertaining thereto to thereby efiect apneumatic compression of said fluid in said main chamber means and thento enter said main chamber means for mechanically increasing the fluidpressure therein, each of said main and auxiliary piston means havingrounded end portions for substantially sliding engagement withrespective adjacent sec tions of said housing means, and each of saidmain and auxiliary piston meanshaving flank sections interconnectingsaid rounded end portions and being arranged on opposite sides of theaxes of rotation thereof, the flank sections of said auxiliary pistonmeans partially corresponding as to their contour to portions of theflank sections of said main piston means and being operable alternatelyto substantially rollingly engage the rounded end portions of therespective main piston means cooperating therewith, and the flanksections of each of said main piston means being operable alternately tosubstantially rollingly engage the rounded end portions of the othermain piston means.

2. A rotary blower according to claim 1, in which that end of eachrounded end portion of each auxiliary piston means which is located infront with regard to the direction of rotation of said auxiliary pistonmeans forms a relatively sharp edge with the adjacent portion of theflank sections of said auxiliary piston means.

3. A rotary blower according to claim 1, in which the distance of theaxis of rotation of each auxiliary piston means from the axis ofrotation of the respective main piston means cooperating therewithequals the distance between the axes of rotation of said two main pistonmeans.

References Cited by the Examiner UNITED STATES PATENTS 1,746,885 2/1930Bunge et al. 230141 2,437,658 3/1948 Williams 230-141 2,691,482 10/1954Ungar 230-141 3,058,652 10/1962 Glamann 230l41 FOREIGN PATENTS 94,75111/1897 Germany. 958,143 5/ 1964 Great Britain.

MARK NEWMAN, Primary Examiner.

WILBUR J. GOODLIN, Examiner.

1. IN A ROTARY BLOWER: HOUSING MEANS HAVING FLUID INLET MEANS AND FLUIDOUTLET MEANS, TWO MAIN PISTON MEANS ROTATABLE WITHIN SAID HOUSING MEANS,AND TWO AUXILIARY PISTON MEANS ROTATABLE WITHIN SAID HOUSING MEANS INAXIALLY SPACED RELATIONSHIP TO SAID MAIN PISTON MEANS AND AT THE SAMESPEED AS THE LATTER FOR RESPECTIVE COOPERATION WITH SAID MAIN PISTONMEANS, SAID MAIN PISTON MEANS BEING ROTATABLE IN OPPOSITE DIRECTION WITHREGARD TO EACH OTHER, AND EACH AUXILIARY PISTON MEANS BEING ROTATABLE INA DIRECTION OPPOSITE TO THE DIRECTION OF ROTATION OF THE RESPECTIVE MAINPISTON MEANS COOPERATING THEREWITH, EACH OF SAID ROTATABLE MAIN PISTONMEANS BEING ADAPTED WITH A RESPECTIVE FIRST SECTION OF SAID HOUSINGMEANS TO FORM MAIN CHAMBER MEANS ADAPTED TO RECEIVE AND ENTRAP FLUIDFROM SAID INLET MEANS, EACH OF SAID AUXILIARY PISTON MEANS BEINGOPERABLE IN RESPONSE TO A FIRST POSITION THEREOF RELATIVE TO THERESPECTIVE MAIN PISTON MEANS COOPERATING THEREWITH TO FORM WITH SAIDMAIN PISTON MEANS AND WITH A RESPECTIVE ADJACENT SECOND SECTION OF SAIDHOUSING MEANS FOR AUXILIARY CHAMBER MEANS ADAPTED TO RECEIVE FLUID FROMSAID OUTLET MEANS, EACH OF AUXILIARY PISTON MEANS ALSO BEING OPERABLEWITH A RESPECTIVE ADJACENT THIRD SECTION OF SAID HOUSING MEANS TO FORMSECOND AUXILIARY CHAMBER MEANS ADAPTED TO RECEIVE AND ENTRAP FLUID FROMSAID OUTLET MEANS, EACH OF SAID AUXILIARY PISTON MEANS BEING OPERABLE INRESPONSE TO A SECOND RELATIVE POSITION THEREOF WITH REGARD TO THERESPECTIVE MAIN PISTON MEANS COOPERATIN THEREWITH TO RELEASE FLUID FROMTHE RESPECTIVE FIRST AUXILIARY CHAMBER MEANS TO THE RESPECTIVE MAINCHAMBER MEANS PERTAINING THERETO TO THEREBY EFFECT A PNEUMATICCOMPRESSION OF SAID FLUID IN SAID MAIN CHAMBER MEANS AND THEN TO ENTERSAID MAIN CHAMBER MEANS FOR MECHANICALLY INCREASING THE FLUID PRESSURETHEREIN, EACH OF SAID MAIN AUXILIARY PISTON MEANS HAVING ROUNDED ENDPORTIONS FOR SUBSTANTIALLY SLIDING ENGAGEMENT WITH RESPECTIVE ADJACENTSECTIONS OF SAID HOUSING MEANS, AND EACH OF SAID MAIN AND AUXILIARYPISTON MEANS HAVING FLANK SECTIONS INTERCONNECTING SAID ROUNDED ENDPORTIONS AND BEING ARRANGED ON OPPOSITE SIDES OF THE AXES OF ROTATIONTHEREOF, THE FLANK SECTIONS OF SAID AUXILIARY PISTON MEANS PARTIALLYCORRESPONDING AS TO THEIR CONTOUR TO PORTIONS OF THE FLANK SECTIONS OFSAID MAIN PISTON MEANS AND BEING OPERABLE ALTERNATELY TO SUBSTANTIALLYROLLINGLY ENGAGE THE ROUNDED END PORTIONS OF THE RESPECTIVE MAIN PISTONMEANS COOPERATING THEREWITH, AND THE FLANK SECTIONS OF EACH OF SAID MAINPISTON MEANS BEING OPERABLE ALTERNATELY TO SUBSTANTIALLY ROLLINGLYENGAGE THE ROUNDED END PORTIONS OF THE OTHER MAIN PISTON MEANS.